Spatial distribution of apatite fission-track ages on the Cretaceous granites of the southern part of Ou Backbone Range; Insights into the doming uplift of a volcanic arc

Fukuda, Shoma   ; Sueoka, Shigeru   ; Kagami, Saya   ; Kajita, Yuya*; Tagami, Takahiro*

To understand geoscientific phenomena (e.g., magmatism, seismicity, and, orogenesis) that occur actively along plate subduction zones at the Earth's surface, a quantitative approach plays a key role in uplift/subsidence and denudation on various timescales to reveal the mechanism of strain release and accumulation. In this study, we focus on the Northeast Japan Arc (NEJA) as an island arc with a typical topographic alighnment, and attempt to estimate the mountain formation process of the Ou Backbone Range (hereinafter, OBR) which locates in the center axis of the NEJA as a volcanic arc, based on thermochronology. It is expected to lead to the proposal of a vertical deformation model for volcanic arcs distributed in the plate subduction zone. We have applied low-temperatures ( 300 degree Celsius) thermochronometric approaches, mainly the apatite fission track and apatite (U-Th)/He (AFT and AHe, respectively) methods, to estimate the uplift of each island arc components (i.e., fore-arc, volcanic arc, back-arc) in the Northeast Japan Arc (NEJA). In this presentation, regarding the spatial distribution of ca. 20 AHe ages (39.1-1.5 Ma) and ca. 10 AFT ages (29.8-4.4 Ma) obtained so far in the southern part of the OBR, which already provided the doming uplift of the OBR, we attempted to obtain new AFT age data in order to expand the data for the blank areas where no ages were reported in order to develop a detailed uplift model. As a result, about 10 new AFT ages were obtained in the southern part of the OBR, ranging from a few tens to a few Ma. These results are consistent with the previously reported AFT ages, and suggest that the ages of a few Ma reflect uplift and denudation associated with strong compressive stress in the east-west direction after 3 to 2 Ma.